Asphalt modifier and asphalt composition comprising the same

ABSTRACT

The present invention relates to an asphalt modifier including a main chain of a vinyl aromatic hydrocarbon-conjugated diene block copolymer, and more particularly, to an asphalt modifier capable of effectively improving low-temperature properties, high-temperature properties, storage stability, and the like of an asphalt composition due to excellent compatibility with the asphalt composition when a vinyl aromatic hydrocarbon-conjugated diene block copolymer containing a certain multifunctional group is used as the asphalt modifier, and an asphalt composition including the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national phase entry under 35 U.S.C. § 371of International Application No. PCT/KR2016/015092 filed on Dec. 22,2016, which claims priority from Korean Patent Application No.10-2016-0137691, filed on Oct. 21, 2016 with the Korean IntellectualProperty Office, the disclosures of which are herein incorporated byreference in its entirety.

TECHNICAL FIELD

The present invention relates to an asphalt modifier having highsolubility and an asphalt composition including the same.

BACKGROUND ART

Asphalt is a residue which is obtained after most of volatile oils incomponents of crude oil are evaporated, and has a physical property ofbeing maintained in a liquid or semi-solid state having a high viscosityat a high temperature but being firmly hardened at a temperature lessthan or equal to room temperature.

Because the asphalt has good plasticity, high water repellency,electrical insulating properties and adhesiveness, and chemically stablecharacteristics, the asphalt has been widely used for constructionmaterials such as paving materials or waterproof materials. However, theasphalt has drawbacks in that plastic deformation occurs during use whenthe asphalt is exposed to a high temperature for a prolonged period oftime and cracking occurs at a low temperature due to external impacts.In order to solve the above problems, research has been conducted toimprove the physical properties of asphalt by adding various polymers.

Specifically, a vinyl aromatic hydrocarbon-conjugated diene blockcopolymer such as a styrene-butadiene-styrene (SBS) block copolymer hasbeen widely used as a modifier for improving the physical properties ofasphalt.

When the vinyl aromatic hydrocarbon-conjugated diene block copolymer isused as the asphalt modifier, much time and cost are required todissolve the block copolymer at a high temperature. Therefore, the mostimportant physical property of the block copolymer used as the asphaltmodifier is compatibility with asphalt.

However, as advancement of oil refining facilities has been continuouslymade due to an increase in oil prices and energy saving policy, theamount of asphaltene in asphalt, as a refining byproduct, has beenincreased. Because the asphaltene as an aggregate of aromatichydrocarbons, includes a large amount of polar functional groups at theends thereof, the asphaltene has very low compatibility with blockcopolymers having no hydrophilic functional groups. Thus, a processingtime or a manufacturing time of the asphalt may not only be remarkablyextended, but a decline in quality of the asphalt, for example, adecrease in elasticity of modified asphalt, may also be caused.

Accordingly, various studies on a method of adjusting a molecular weightof the SBS block copolymer or changing a microstructure of the SBS blockcopolymer to provide a coupling effect, or a method of adding anadditive, such as oil, as a processing aid have been conducted toenhance the compatibility with the asphalt.

By way of example, Korean Patent Publication No. 2016-0052310 disclosesthat compatibility with the asphalt and physical properties of theasphalt may be improved when a vinyl aromatic hydrocarbon-conjugateddiene block copolymer including a predetermined content of aheterologous conjugated diene block having a peak molecular weight Mp isused as an asphalt modifier.

Also, Korean Patent Publication No. 2015-0102869 discloses thatmodification workability, low-temperature properties and storagestability of the asphalt may be improved when a functionalized vinylaromatic hydrocarbon-conjugated diene block copolymer in which analdehyde group is bound to a main chain of a conjugated diene block isused as an asphalt modifier.

Such patents have somewhat improved mixing property with the asphalt,but do not exhibit a sufficient improvement effect. Also, the patentshave no ultimate solution because there is a high variation in qualityof asphalt and asphalt compositions obtained accordingly also havedifferent modification effects. Thus, there is an urgent need forresearch on a vinyl aromatic hydrocarbon-conjugated diene blockcopolymer having excellent compatibility and modifying performance asthe asphalt modifier.

PRIOR-ART DOCUMENTS

[Patent Documents]

Korean Patent Publication No. 2016-0052310 (May 12, 2016), “AsphaltModifier and Asphalt Composition Comprising the Same”

Korean Patent Publication No. 2015-0102869 (Sep. 8, 2015),“Functionalized Vinyl Aromatic Hydrocarbon-Conjugated Diene BlockCopolymer Composition, Method of Preparing the Same and AsphaltComposition Comprising the Same”

DISCLOSURE Technical Problem

Accordingly, the present inventors have conducted research on a methodof improving solubility of an asphalt modifier without changing amolecular microstructure of an SBS copolymer as a conventional modifier,and found that solubility in asphalt may be remarkably improved only byintroducing a silane group containing an alkyl group as a coupling agentinto an end of the SBS copolymer. Therefore, the present invention hasbeen completed based on the facts.

Accordingly, it is an aspect of the present invention to provide anasphalt modifier having a novel structure.

It is another aspect of the present invention to provide an asphaltcomposition including the asphalt modifier.

Technical Solution

To solve the above problems, according to an aspect of the presentinvention, there is provided an asphalt modifier which is represented bythe following Formula 1 and comprises a multifunctional group bound to amain chain of a vinyl aromatic hydrocarbon-conjugated diene blockcopolymer:

wherein A, B, C, X, m, n, o, and p are as described in thisspecification.

According to another aspect of the present invention, there is providedan asphalt composition including the asphalt modifier.

Advantageous Effects

The asphalt modifier according to the present invention has excellentcompatibility with asphalt as a certain multifunctional group isintroduced into a vinyl aromatic hydrocarbon-conjugated diene blockcopolymer. Thus, when the asphalt modifier is used in an asphaltcomposition, workability can be remarkably improved, and variousphysical properties of asphalt, such as low-temperature andhigh-temperature properties, storage stability, and the like, can beeffectively improved.

BEST MODE

Hereinafter, the present invention will be described in further detail.

The terms and/or words used in this specification and the appendedclaims are not to be interpreted as limited to commonly used meanings ormeanings in dictionaries and should be interpreted with meanings andconcepts which are consistent with the technological scope of thepresent invention based on the principle that the present inventors haveappropriately defined concepts of terms to describe the presentinvention in the best way.

To improve physical properties of an asphalt composition, a vinylaromatic hydrocarbon-conjugated diene block copolymer is used as anasphalt modifier.

The asphalt composition is mainly composed of four components. Amongthese, a component having the worst compatibility with a vinyl aromatichydrocarbon-conjugated diene block copolymer used as the asphaltmodifier is asphaltene. Asphaltene is a highly concentrated aromatichydrocarbon compound including polar functional groups having a numberof heteroatoms in a chemical aspect. However, because the vinyl aromatichydrocarbon-conjugated diene block copolymer used as the asphaltmodifier contains no polar functional groups, the asphalt modifier haspoor compatibility with an asphalt composition, resulting in degradedprocessability and workability. Also, the asphalt modifier is notsufficiently mixed with the asphalt composition, resulting in degradedquality, such as degraded elasticity, of asphalt.

To solve the above problems, a method of adjusting a molecular weight ofa block copolymer or a method of adding a hydrophilic monomer, oil, andthe like has been used in the related art. However, such a method has adrawback in that the molecular weight of the block copolymer maydecrease due to cleavage of chains thereof, and thus the physicalproperties of the asphalt composition may be rather degraded.

Accordingly, in the present invention, there is provided an asphaltmodifier including a vinyl aromatic hydrocarbon-conjugated diene blockcopolymer into which a certain multifunctional group is introduced tosecure excellent compatibility when mixed in the asphalt composition.

Specifically, the asphalt modifier according to the present inventionmay include a main chain of a vinyl aromatic hydrocarbon-conjugateddiene block copolymer and a multifunctional group bound to the mainchain of the vinyl aromatic hydrocarbon-conjugated diene blockcopolymer, and may be represented by the following Formula 1:

wherein A to C blocks are each independently a vinyl aromatichydrocarbon block or a conjugated diene block, X is represented by thefollowing Formula 2, m, n, and o are each an integer greater than orequal to 1, and p is an integer in a range of 0<p≤3;

wherein Y₁ to Y₄ are the same or different from each other, and eachrepresent a halogen element,

q to t are each an integer of 0 or 1, provided that at least one of q tot is an integer of 1,

R₁ is a C1 to C4 alkyl group,

R₂ is a C1 to C10 alkyl group, and

* is a moiety of a multifunctional group that may be bound to a vinylaromatic hydrocarbon block or conjugated diene block unit in the vinylaromatic hydrocarbon-conjugated diene block copolymer, where one and twomolecules of the vinyl aromatic hydrocarbon-conjugated diene blockcopolymer may be bound to one molecule of the multifunctional group.

According the present invention, the vinyl aromatic hydrocarbon blockmay have a structure derived from a vinyl group-containing C6 to C30aromatic hydrocarbon-based compound. For example, the vinyl aromatichydrocarbon block may include at least one selected from the groupconsisting of styrene, α-methylstyrene, 3-methylstyrene,4-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, and4-(para-methylphenyl)styrene.

The conjugated diene block may have a structure derived from abutadiene-based compound. For example, the conjugated diene block mayinclude at least one selected from the group consisting of1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and 2-phenyl-1,3-butadiene.

More preferably, styrene or methylstyrene may be used as the vinylaromatic hydrocarbon alone or in combination thereof, and butadiene orisoprene may be used as the conjugated diene alone or in combinationthereof.

In this case, the vinyl aromatic hydrocarbon block and the conjugateddiene block may be present at a weight ratio of 1:1 to 1:4. When theweight ratio is included within this range, the vinyl aromatichydrocarbon block and the conjugated diene block may be stably dissolvedin the asphalt composition, thereby achieving a sufficient modificationeffect. When the content of the vinyl aromatic hydrocarbon is less thanthis content range, physical properties of asphalt may be degradedbecause the vinyl aromatic hydrocarbon block does not easily form aphysical cross-linking point. On the other hand, when the content of thevinyl aromatic hydrocarbon is greater than this content range,solubility in asphalt may be poor, and low-temperature properties may bedegraded.

Also, the block copolymer represented by a [A-B-C] block may have aweight average molecular weight of 30,000 to 500,000 g/mol, preferably35,000 to 300,000 g/mol, and may be linear, branched, or a combinationthereof. When the molecular weight of the vinyl aromatichydrocarbon-conjugated diene block copolymer is less than this range,high-temperature properties may be degraded due to a very low molecularweight of the vinyl aromatic hydrocarbon block. On the other hand, whenthe molecular weight of the vinyl aromatic hydrocarbon-conjugated dieneblock copolymer is greater than this range, solubility in asphalt may beseverely poor.

In this case, a linear, branched, symmetric, asymmetric, or radialstyrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), orstyrene-butadiene (SB) diblock copolymer may be used as the blockcopolymer represented by the [A-B-C] block. The block copolymers may beused alone or in combination of two or more. More preferably,styrene-butadiene-styrene (SBS) is used.

In particular, the asphalt modifier according to the present inventionincludes the multifunctional group X represented by Formula 2 bound to amain chain of the vinyl aromatic hydrocarbon-conjugated diene blockcopolymer.

The multifunctional group X is derived from a coupling agent.Specifically, the multifunctional group X may be formed by a reaction ofa coupling agent and a vinyl aromatic hydrocarbon-conjugated diene blockcopolymer, which may be used as the asphalt modifier, in the presence ofan organic metal compound or a living anion that is a polymer chainhaving an anionic end initiated from a polymerization initiator. Inparticular, a reaction of the asphalt modifier with a polar grouppresent in asphalt is promoted under a high-temperature condition byintroducing the multifunctional group X represented by Formula 2 intothe main chain of the vinyl aromatic hydrocarbon-conjugated diene blockcopolymer. According to this, the asphalt modifier of the presentinvention serves to enhance compatibility with the asphalt composition.Also, because the asphalt modifier is uniformly mixed in the asphaltcomposition, an effect of improving the physical properties of theasphalt composition by addition of the asphalt modifier may besufficiently achieved.

X is represented by Formula 2, where the alkyl group of R₁ in Formula 2is methyl, ethyl, propyl, isopropyl, or butyl, preferably methyl.

Also, the alkyl group of R₂ may be a C1 to C10 linear or branched alkylgroup, preferably a linear alkyl group such as methyl, ethyl, propyl,butyl, pentyl, hexyl, heptyl, octyl, nonyl, decenyl, or the like. Morepreferably, the alkyl group of R₂ may be propyl or butyl. Also, when tis 1, the alkyl group of R₂ may be in the form of an alkylene group fromwhich one hydrogen atom is excluded.

When such a functional group has a structural difference todichlorodimethylsilane (DMDCS) often used as a conventional couplingagent, R₂ in the functional group X contains an alkyl group having oneor more carbon atoms, preferably 3 or more carbon atoms, compared toDMDCS containing only a methyl group.

In particular, in the asphalt modifier of the present invention, thehalogenated alkyl group serves to enhance reactivity of the asphaltmodifier of Formula 1 with a polar group of asphalt via X. Therefore, Xhas at least one halogenated alkyl group to impart high reactivity withthe polar group of asphalt, compared the DMDCS in which only two methylgroups are present, which has been used as the conventional couplingagent. On the other hand, the multifunctional group X exhibits superiorcompatibility, compared to the DMDCS having low reactivity with thepolar group of asphalt. Such compatibility also results in increasedsolubility. Solubility characteristics may be determined by a phaseseparation test. Referring to Table 1 to be described below, it can beseen that a significant increase in solubility may be achieved, comparedto the use of the asphalt modifier modified with DMDCS.

In the asphalt modifier of the present invention, a content of themultifunctional group X may be in a range of 40 to 4,700 ppm, preferablyin a range of 100 to 3,500 ppm, based on the total weight 1 of the vinylaromatic hydrocarbon-conjugated diene block copolymer. When the contentof the multifunctional group is included within this range,compatibility with asphalt may be enhanced, and the physical properties,such as an operating temperature range, lifespan, and the like, of theasphalt containing the multifunctional group may be improved.

Also, the present invention provides a method of preparing theaforementioned asphalt modifier.

The method of preparing an asphalt modifier according to the presentinvention includes preparing a vinyl aromatic hydrocarbon block bypolymerizing a vinyl aromatic hydrocarbon-based monomer in ahydrocarbon-based solvent using a polymerization initiator; preparing avinyl aromatic hydrocarbon-conjugated diene block copolymer by mixing apolymerization initiator and a conjugated diene monomer with the vinylaromatic hydrocarbon block and polymerizing the resulting mixture; andcoupling a multifunctional group to the vinyl aromatichydrocarbon-conjugated diene block copolymer by mixing a coupling agentwith the vinyl aromatic hydrocarbon-conjugated diene block copolymer.

Hereinafter, respective steps of the method will be described in detail.

First, a vinyl aromatic hydrocarbon block is prepared by polymerizing avinyl aromatic hydrocarbon-based monomer in a hydrocarbon-based solventusing a polymerization initiator.

As described above, the vinyl aromatic hydrocarbon-based monomer mayinclude a vinyl group-containing C6 to C30 aromatic hydrocarbon-basedcompound. The vinyl aromatic hydrocarbon-based monomer may be used at aproper amount in consideration of the content of the vinyl aromatichydrocarbon block in the finally prepared vinyl aromatichydrocarbon-conjugated diene block copolymer.

The hydrocarbon-based solvent does not react with a polymerizationinitiator to be described below. In this case, types of thehydrocarbon-based solvent may be used without particular limitation aslong as they are generally used for a polymerization reaction. Forexample, the hydrocarbon-based solvent may include at least one selectedfrom the group consisting of linear or branched hydrocarbon compoundssuch as butane, n-pentane, n-hexane, n-heptane, isooctane, and the like;alkyl-substituted or unsubstituted cyclic hydrocarbon compounds such ascyclopentane, cyclohexane, cycloheptane, methyl cyclohexane, methylcycloheptane, and the like; and alkyl-substituted or unsubstitutedaromatic hydrocarbon compounds such as benzene, toluene, xylene,naphthalene, and the like.

Also, the hydrocarbon solvent may further include a polar solvent toadjust a content of vinyl during polymerization of the conjugated dienemonomer and enhance a polymerization rate. For example, the polarsolvent may include one or more selected from the group consisting oftetrahydrofuran, ethyl ether, tetramethylethylene diamine, andbenzofuran.

The polymerization initiator may be used without particular limitationas long as they may be generally used for anionic polymerization.

The polymerization initiator may be an organic metal compound or aliving anion that is a polymer chain having an anionic end initiatedfrom the polymerization initiator.

The organic metal compound may be an organic lithium compoundrepresented by the following Formula 3:R₃—Li  [Formula 3]

wherein R₃ is a C1 to C20 aliphatic, alicyclic, alkyl-substitutedalicyclic, aromatic, or alkyl-substituted aromatic hydrocarbon group.

For example, the organic metal compound may include at least oneselected from the group consisting of n-butyllithium, sec-butyllithium,tert-butyllithium, methyllithium, ethyllithium, isopropyllithium,cyclohexyllithium, allyllithium, vinyllithium, phenyllithium, andbenzyllithium.

Next, a vinyl aromatic hydrocarbon-conjugated diene block copolymer isprepared by mixing a polymerization initiator and a conjugated dienemonomer with the vinyl aromatic hydrocarbon block and polymerizing theresulting mixture.

As described above, the conjugated diene monomer may be abutadiene-based compound. The conjugated diene monomer may be used at aproper amount in consideration of the content of the conjugated dieneblock in the finally prepared vinyl aromatic hydrocarbon-conjugateddiene block copolymer.

Like the aforementioned step, the polymerization of the conjugated dienemay also be performed through an anionic polymerization reaction.Therefore, the polymerization initiator is as described above.

In the aforementioned two-step polymerization reaction, thepolymerization initiator may be included at a content of 0.3 to 3.3mmol, based on the total content of the vinyl aromatichydrocarbon-conjugated diene block copolymer. When the content of thepolymerization initiator is less than this content range, stirringefficiency of a reactor may be declined due to an excessive increase inmolecular weight of the block copolymer, and thus a reaction with acoupling agent to be described below does not easily occur, which makesit difficult to introduce a multifunctional group. On the other hand,when the content of the polymerization initiator is greater than thiscontent range, productivity may be severely lowered in subsequentprocesses.

The polymerization reaction is preferably performed at 0 to 150° C. in apressure range (0.1 to 10 bar), in which a reaction product may bemaintained in a liquid phase, until a consumption rate of the conjugateddiene monomer reaches 99% or more.

Also, the vinyl aromatic hydrocarbon-conjugated diene block copolymer inwhich the aforementioned vinyl aromatic hydrocarbon block and conjugateddiene block are alternately aligned is prepared through thepolymerization reaction. In this case, at least one of the A to C blocksin Formula 1 preferably includes the vinyl aromatic hydrocarbon block.

Then, the multifunctional group is coupled to the vinyl aromatichydrocarbon-conjugated diene block copolymer by mixing a coupling agentwith the vinyl aromatic hydrocarbon-conjugated diene block copolymer.

The coupling reaction is carried out by introducing the multifunctionalgroup X represented by Formula 2 into the main chain of the vinylaromatic hydrocarbon-conjugated diene block copolymer represented byFormula 1, and simultaneously connecting conjugated diene blocks betweenthe block copolymers.

In this case, the coupling agent may be a compound represented by thefollowing Formula 4:

wherein Y₁ to Y₄, R₁ and R₂, and q to t are as described above.

More specifically, the coupling agent may include (2-chloroethyl)methyldichlorosilane (1), (3-chloropropyl)methyl dichlorosilane (2),(4-chlorobutyl)methyl dichlorosilane (3), (3-chloropropyl)propyldichlorosilane (4), bis(3-chloropropyl) dichlorosilane (5), anddichloro(chloromethyl) methylsilane (6), which are represented by thefollowing formulas, respectively. Preferably, 3-chloropropylmethyldichlorosilane is used.

Specifically, the coupling agent may be used at a content of 40 ppm to4,700 ppm in a fourth mixed solution.

The aforementioned coupling agent may react with an anionic active siteof an end of a second conjugated diene block in the vinyl aromatichydrocarbon-first conjugated diene-second conjugated diene triblockcopolymer prepared in step 3 to connect the conjugated diene blocksbetween the block copolymers, and may simultaneously perform afunctionalization reaction.

As a result of the aforementioned coupling reaction, the vinyl aromatichydrocarbon-conjugated diene block copolymer of Formula 1 is prepared.In this case, the aromatic hydrocarbon-conjugated diene block copolymerof Formula 3, which is not subjected to the coupling reaction, may bepresent in a state in which the block copolymer is mixed with theproduct obtained as a result of the coupling reaction.

Also, the method of preparing an asphalt modifier according to oneembodiment of the present invention may optionally further includeadding a polymerization terminator such as water or an alcohol into areactor after the coupling reaction to remove the activity of an activepolymer.

Further, the present invention provides a modified asphalt compositionincluding the asphalt modifier represented by Formula 1, asphalt, and across-linking agent.

Asphalt is obtained as a residue when crude oil is refined, mainlyconsists of hydrogen and carbon atoms, and includes a hydrocarboncompound to which a small amount of nitrogen, sulfur, or oxygen atomsare bound. The asphalt includes straight asphalt, cutback asphalt, gussasphalt, blown asphalt, emulsified asphalt, PG-grade asphalt, and thelike.

The straight asphalt is a final residual fraction that is obtained bydistilling a crude oil in a crude distillation unit (CDU) andre-distilling an atmospheric residue (AR) under reduced pressure, andthus contains a large amount of undecomposed bituminous substances.Thus, the straight asphalt may be used as various petroleum-basedasphalt sources. Commercially available straight asphalt includes AP-3,AP-5, and the like, all of which are provided by SK Energy Co., Ltd. orGS Caltex Corp.

In the present invention, the copolymer represented by Formula 1 is usedas the asphalt modifier to improve solubility of asphalt.

Specifically, the modified asphalt composition provided in the presentinvention may include 1 to 10 parts by weight of the asphalt modifier,87 to 98.95 parts by weight of the asphalt, and 0.05 to 3 parts byweight of the cross-linking agent.

Within the above ranges, excellent storage stability of the asphaltcomposition may be secured. When the content of the asphalt modifier isgreater than this content range, an increase in manufacturing costs ofthe modified asphalt composition may be caused. When the content of thecross-linking agent is greater than this content range, elasticity ofmodified asphalt may be lost due to an excessive cross-linking reaction,and the modified asphalt may be gelled. On the other hand, when thecontent of each of the asphalt modifier and the cross-linking agent isless than this content range, high-temperature properties and elasticityof the modified asphalt may be deteriorated due to a low degree ofasphalt modification.

In this case, the asphalt may include 1 to 40% by weight, specifically 5to 30% by weight of asphaltene, based on the total content of theasphalt.

According to the present invention, the asphalt modifier of Formula 1,the cross-linking agent, and the asphalt are mixed with asphalt using ahigh-speed shear mixer to obtain a modified asphalt composition.

The cross-linking agent is not particularly limited as long as thecross-linking agent is a sulfur compound containing sulfur or ironsulfate. For example, a representative example of the sulfur compoundmay be a sulfur element.

When the asphalt composition includes approximately 4 to 5% by weight ofthe modifier under a vulcanization condition, the asphalt compositionpreferably has a melting rate of 1 to 10 hours, more preferably amelting rate of 1 to 8 hours within this weight range. That is, thebalance of the physical properties of the asphalt composition may beeffectively made within this range.

A procedure of blending the modified asphalt composition is as follows.First, asphalt is put into a 1 L heating mantle, and kept at atemperature of 150 to 170° C., preferably 160 to 165° C. for 30 minutesto 2 hours, preferably 40 minutes or more. When the asphalt issufficiently melted, the aforementioned asphalt modifier of Formula 1 isadded to the asphalt while slowly increasing a stirring rate. While arotary speed of the high-speed shear mixer is maintained at 2,500 rpm,the resulting mixture is stirred for 30 to 2 hours, preferably 1 hour bycontrolling a temperature of 180 to 195° C., preferably 190° C.Thereafter, the mixture is transferred to an impeller-type agitator, andstirred at the same temperature for another 5 hours or more, preferably6 to 8 hours while the rotary speed of the high-speed shear mixer ismaintained at 250 rpm. Then, the modified asphalt composition is sampledat points of time to measure physical properties. Also, the modifiedasphalt composition thus prepared is sampled by blending times, andadded to aluminum tubes, which are stored for a predetermined time in a180° C. oven. Then, the solubility is determined as a difference insoftening point between an upper bed and a lower bed of each of thealuminum tubes.

The modified asphalt composition of the present invention may have asoftening point of 65° C., an elongation of 20 cm or more, and aviscosity of 3,000 cPs or less. In this case, the elongation andviscosity are not limited to any certain ranges. For example, theelongation is greater than or equal to 20 cm because the higher theelongation is, the better it is. The viscosity is less than or equal to3,000 cPs because the lower the viscosity is, the more desirable it is.For example, the elongation may be in a range of 20 cm to 80 cm, and theviscosity may be in a range of 300 cPs to 3,000 cPs, but the presentinvention is not limited thereto.

MODE FOR INVENTION

Hereinafter, examples of the present invention will be described indetail so that a person having ordinary skill in the art to which thepresent invention belongs can easily put the present invention intopractice. However, it should be understood that the present inventioncan be implemented in various different forms, and is not limited to theembodiments disclosed below.

Example 1: Preparation of Asphalt Modifier and Asphalt Composition

(1) Preparation of Asphalt Modifier

4.286 g of purified cyclohexane and 273 g of styrene were put into a 10L reactor whose atmosphere was replaced with nitrogen, and warmed to 60°C. while stirring. Thereafter, 1.137 g of n-butyllithium was added tothe mixed solution of cyclohexane and styrene at 60° C. to polymerize astyrene block. Then, 607.5 g of butadiene was added thereto, andpolymerized until the butadiene was completely consumed.

After the polymerization reaction was completed, 2.213 g of3-chloropropylmethyl dichlorosilane (CPMDS) as a coupling agent wasadded thereto, and a coupling reaction was then performed to prepare apolymer in which the chloropropylmethyl dichlorosilane was substitutedwith a terminal butadiene group.

Subsequently, 0.2 g of water as a reaction terminator was added to themixed solution to remove reaction activity. Thereafter, 6.16 g of asolution obtained by mixing first and second antioxidants with the mixedsolution was added to a polymerization solution to prepare a linearstyrene-butadiene block copolymer having a weight average molecularweight of approximately 110 kg/mol and a styrene block content of 31% byweight.

In this case, the weight average molecular weight was measured bydissolving each polymer pellet sample in tetrahydrofuran (THF) for 30minutes, loading the sample onto gel permeation chromatography (GPC,Waters Corp.) to flow therethrough, and comparing a molecular weight ofthe sample with a reference molecular weight of a polystyrene (PS)standard.

Next, a stripping process was generally performed to recover only thepolymer from the reaction solution. Specifically, 0.7 g of Tamol (BASF)as a dispersing agent, and 0.5 g of CaCl₂ were added to 3 L of water,and boiled. Then, the polymer solution was slowly added to the boilingwater so that the polymer was aggregated in water. Thereafter, theaggregated polymer was dispersed with a size of 1 to 20 mm in water, andthen recovered by evaporating the solvent. The recovered polymer wasdried for 16 hours in a 60° C. oven to prepare a functionalizedstyrene-butadiene block copolymer pellet.

(2) Preparation of Asphalt Composition

500 g of asphalt (AP3, SK Corp.) was added to a heating mantle, and eachof the asphalt modifiers thus prepared was added in an amount of 4.8% byweight based on the total weight of the asphalt composition whilestirring at a high shear rate of 2,500 rpm at 190° C.

After an hour, 0.53 g of sulfur as a cross-linking agent was addedthereof, and stirred at a low shear rate of 200 rpm. In this case, whilethe resulting mixture was observed under a fluorescence microscope, themixture was stirred until an SBS copolymer was dissolved, thereby toprepare an asphalt composition.

Example 2: Preparation of Asphalt Modifier and Asphalt Composition

An asphalt modifier and an asphalt composition were prepared in the samemanner as in Example 1, except that bis(3-chloropropyl) dichlorosilanewas used as the coupling agent instead of the CPMDS.

Example 3: Preparation of Asphalt Modifier and Asphalt Composition

An asphalt modifier and an asphalt composition were prepared in the samemanner as in Example 1, except that dichloro(chloromethyl) methylsilanewas used as the coupling agent instead of the CPMDS.

Comparative Example 1: Preparation of Asphalt Modifier and AsphaltComposition

An asphalt modifier and an asphalt composition were prepared in the samemanner as in Example 1, except that dichlorodimethylsilane (DMDCS) wasused as the coupling agent instead of the CPMDS.

Experimental Example 1: Evaluation of Physical Properties of AsphaltCompositions

The physical properties of the modified asphalt composition includingeach of the asphalt modifiers prepared in Examples and ComparativeExample were measured, as follows. The results are listed in thefollowing Table 1.

(1) Softening Point

The softening point is a measure of high-temperature properties of themodified asphalt measured according to the American Society for Testingand Materials (ASTM) D36. Here, the softening point was measured byheating water or glycerin at a rate of 5° C./minute so that a specimenbegan to soften by the heating, followed by measuring a temperature whena ball having a diameter of 9.525 mm and a weight of 3.5 g, which hadbeen disposed on the specimen, moved down by approximately 1 inch.

(2) Phase Separation Temperature

50 g of the modified asphalt composition was weighed in an aluminumtube, and kept for 72 hours in a 180° C. oven. Thereafter, the asphaltcomposition was divided into three equal parts, and softening points ofthe top and bottom parts were then measured according to the ASTM D36method. Then, a temperature difference between the top and bottom partswas calculated.

(3) Viscosity

The viscosity was measured at 135° C., 160° C. and 180° C. according toASTM D4402 under the conditions of Spindle #27 using Brookfield DV-II+Pro Model.

(4) Elastic Recovery Rate

The elastic recovery rate was measured according to ASTM D6083-97 aftera specimen is kept at 25° C. for an hour.

TABLE 1 Stirring time Comparative Items (hour) Example 1 Example 2Example 3 Example 1 Softening point (° C.) 6 86.1 86.3 86.9 88.0 7 85.385.3 86.2 87.2 8 84.2 83.5 85.2 86.5 Phase separation 6 5.0 5.5 5.0 23.3temperature (ΔT, ° C.) 7 1.3 0.9 1.8 8.5 8 0.2 1.0 1.2 2.9 Viscosity(cps) 8 135° C. 1865 1830 1810 1860 160° C. 630 625 615 665 180° C. 320310 315 335 Elastic recovery rate (%) at 25° C. 94.8 95.8 94.5 96.0

As listed in Table 1, it can be seen that the asphalt modifier hadremarkably improved solubility in the asphalt composition because themodified asphalt composition including the asphalt modifier according tothe present invention had a very low phase separation temperaturewithout degrading the basic physical properties of modified asphalt,such as a softening point, viscosity, elongation, and an elasticrecovery rate, compared to the modified asphalt composition ofComparative Example 1.

Also, it can be seen that the manufacturing time of the modified asphaltcomposition of Example 1 including the styrene butadiene block copolymerinto which a certain multifunctional group was introduced according tothe present invention was shortened by approximately 1 to 1.5 hours,compared to the modified asphalt composition of Comparative Example 1.

Generally, it is contemplated that phase separation does not occur whenthe phase separation temperature is less than or equal to 2.5° C. Thus,it can be seen that the asphalt modifier was completely dissolved in theasphalt composition because the phase separation temperatures inExamples were in a range of 0.2 to 1.5° C. when the stirring times were7 hours and 8 hours. From the results, it can be seen that the modifiedasphalt composition had excellent storage stability.

INDUSTRIAL APPLICABILITY

The asphalt modifier of the present invention has excellentcompatibility with the asphalt composition, and thus the asphaltcomposition having excellent low-temperature and high-temperatureproperties, storage stability, and modification workability can beprovided.

The invention claimed is:
 1. An asphalt modifier comprising amultifunctional group bound to a main chain of a vinyl aromatichydrocarbon-conjugated diene block copolymer represented by thefollowing Formula 1:

wherein A to C blocks are each independently a vinyl aromatichydrocarbon block or a conjugated diene block, m, n, and o are each aninteger greater than or equal to 1, p is an integer in a range of 0<p≤3,and a multifunctional group X is derived from a coupling agent, whereinthe coupling agent comprises at least one of (2-chloroethyl)methyldichlorosilane, (3-chloropropyl)methyl dichlorosilane,(4-chlorobutyl)methyl dichlorosilane, (3-chloropropyl)propyldichlorosilane, bis(3-chloropropyl) dichlorosilane, ordichloro(chloromethyl) methylsilane.
 2. The asphalt modifier accordingto claim 1, wherein the vinyl aromatic hydrocarbon block comprises atleast one selected from the group consisting of styrene,α-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene,4-cyclohexylstyrene, and 4-(para-methylphenyl) styrene.
 3. The asphaltmodifier according to claim 1, wherein the conjugated diene blockcomprises at least one selected from the group consisting of1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and 2-phenyl-1,3-butadiene.4. The asphalt modifier according to claim 1, wherein X is included atan amount of 40 to 4,700 ppm, based on the total weight 1 of the blockcopolymer.
 5. The asphalt modifier according to claim 1, wherein theblock copolymer has a weight average molecular weight of 30,000 to500,000 g/mol.
 6. A method of preparing an asphalt modifier of claim 1,comprising: preparing a vinyl aromatic hydrocarbon block by polymerizinga vinyl aromatic hydrocarbon-based monomer in a hydrocarbon-basedsolvent using a polymerization initiator; preparing a vinyl aromatichydrocarbon-conjugated diene block copolymer by mixing a polymerizationinitiator and a conjugated diene monomer with the vinyl aromatichydrocarbon block and polymerizing the resulting mixture; and performinga coupling reaction by mixing a coupling agent with the vinyl aromatichydrocarbon-conjugated diene block copolymer, wherein the coupling agentcomprises (2-chloroethyl)methyl dichlorosilane, (3-chloropropyl)methyldichlorosilane, (4-chlorobutyl)methyl dichlorosilane,(3-chloropropyl)propyl dichlorosilane, bis(3-chloropropyl)dichlorosilane, or dichloro(chloromethyl) methylsilane.
 7. An asphaltcomposition comprising asphalt, a cross-linking agent, and an asphaltmodifier, wherein the asphalt modifier is the asphalt modifier of claim1.